The integration of a microphone function and a pressure sensor function in one shared MEMS chip contributes to the miniaturization of application boards and terminal equipment while simultaneously increasing the functional scope, which is increasingly gaining significance in the area of consumer electronics.
A component including a microphone function and a pressure sensor function, which is implemented in the form of a chip stack, is discussed in WO 2012/122872 A1.
This chip stack includes a MEMS element, the microphone structure including microphone diaphragm, acoustically permeable counter-element and microphone capacitor being formed in its layer structure, as well as the pressure sensor diaphragm including the deflectable electrode of the measuring capacitor. Two access openings are formed in the rear side of the MEMS element, one for the microphone structure and one for the pressure sensor diaphragm, the access openings being situated adjacent to one another in the layer structure of the MEMS element. Furthermore, the chip stack of the known component includes a cap wafer, which is mounted face-to-face on the MEMS element. In the layer structure of the cap wafer a recess is formed, which is situated above the microphone structure and forms a closed rear side volume for the microphone function. Moreover, a fixed counter-electrode is provided in the layer structure of the cap wafer, which is situated above the deflectable electrode of the pressure sensor structure and together with it, forms the measuring capacitor of the pressure sensor structure.
The component concept of WO 2012/122872 A1 provides for structuring the microphone diaphragm and the pressure sensor diaphragm from the same functional layer of the MEMS layer structure. The deflectable electrode of the pressure sensor structure is situated here on a carrier element, which is centrally and rigidly connected to the deflectable pressure sensor diaphragm. This carrier element is structured from the same functional layer as the counter-element of the microphone structure.
This component concept is believed to be problematic since the distance between the electrodes of the measuring capacitor of the pressure sensor structure is defined only within the scope of the assembly and packaging technology (APT), i.e., only when the MEMS element and the cap wafer are joined to one another. Generally, the electrodes of the measuring capacitor should have a certain predefined distance. This makes special demands on the APT of the component and is consequently connected with increased manufacturing expense. Moreover, this significantly increases the susceptibility to error of the manufacturing process.